I'm a healer and you learn at which packs you can drink 50% mana and at which not. It's rare that you have to stop the group to drink.
Good tanks either wait when you need to drink or they pull small packs.
If the tank pulls 5 big packs after each other and won't let you drink just let him die.
But you shouldn't need to stop the group to drink more than 3 times in a dungeon.